U.S. patent number 8,179,660 [Application Number 11/935,854] was granted by the patent office on 2012-05-15 for electronic device and method for manufacturing the same.
This patent grant is currently assigned to Murata Manufacturing Co., Ltd.. Invention is credited to Hiroshi Katsube, Jun Nishikawa.
United States Patent |
8,179,660 |
Katsube , et al. |
May 15, 2012 |
**Please see images for:
( Certificate of Correction ) ** |
Electronic device and method for manufacturing the same
Abstract
A highly reliable electronic device that prevents entry of a
plating solution via an external electrode and entry of moisture of
external environment inside thereof, and generates no soldering
defects or solder popping defects which are caused by precipitation
of a glass component on a surface of the external electrode. The
electrode structure of the electronic device is formed of Cu-baked
electrode layers primarily composed of Cu, Cu plating layers formed
on the Cu-baked electrode layers and which are processed by a
recrystallization treatment, and upper-side plating layers formed
on the Cu plating layers. After the Cu plating layers are formed, a
heat treatment is performed at a temperature in the range of a
temperature at which the Cu plating layers are recrystallized to a
temperature at which glass contained in a conductive paste is not
softened, so that the Cu plating layers are recrystallized.
Inventors: |
Katsube; Hiroshi (Echizen,
JP), Nishikawa; Jun (Fukui, JP) |
Assignee: |
Murata Manufacturing Co., Ltd.
(Nagaokakyo-Shi, Kyoto-fu, JP)
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Family
ID: |
37481471 |
Appl.
No.: |
11/935,854 |
Filed: |
November 6, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080081200 A1 |
Apr 3, 2008 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/JP2006/310389 |
May 24, 2006 |
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Foreign Application Priority Data
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Mar 6, 2005 [JP] |
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2005-164841 |
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Current U.S.
Class: |
361/306.1;
361/308.1; 361/306.3; 361/310; 361/309 |
Current CPC
Class: |
H01G
4/2325 (20130101); H01G 4/30 (20130101); Y10T
428/31678 (20150401) |
Current International
Class: |
H01G
4/00 (20060101) |
Field of
Search: |
;361/306.1,306.3,308.1,309,310 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 178 024 |
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Feb 2002 |
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EP |
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57-93517 |
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Jun 1982 |
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JP |
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03-077306 |
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Apr 1991 |
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JP |
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04-171912 |
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Jun 1992 |
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JP |
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07-057959 |
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Mar 1995 |
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JP |
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7-335486 |
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Dec 1995 |
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JP |
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8-264371 |
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Oct 1996 |
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JP |
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10-92602 |
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Apr 1998 |
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JP |
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2000-100647 |
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Apr 2000 |
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JP |
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2001-230151 |
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Aug 2001 |
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JP |
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2004-55679 |
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Feb 2004 |
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JP |
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2004-172383 |
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Jun 2004 |
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JP |
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2005-64494 |
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Mar 2005 |
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JP |
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2005-164841 |
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Jun 2005 |
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JP |
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Other References
International Search Report PCT/JP2006/310389 dated Jun. 20, 2006.
cited by other .
Written Opinion PCT/JP2006/310389 dated Jun. 20, 2006. cited by
other.
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Primary Examiner: Lam; Cathy
Attorney, Agent or Firm: Dickstein Shapiro LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
The present application is a continuation of International
Application No. PCT/JP2006/310389, filed May 24, 2006, which claims
priority to Japanese Patent Application No. JP2005-164841, filed
Jun. 3, 2005, the entire contents of each of these applications
being incorporated herein by reference in their entirety.
Claims
The invention claimed is:
1. An electronic device comprising: an electronic device main body;
and an external electrode formed on a surface of the electronic
device main body, wherein the external electrode includes: a
Cu-baked electrode layer primarily composed of Cu; a
recrystallization treated Cu plating layer formed on the Cu-baked
electrode layer; and at least one upper-side plating layer formed
on the Cu plating layer.
2. The electronic device according to claim 1, wherein the
electronic device main body includes a ceramic sintered body and an
internal electrode disposed therein, and the external electrode is
electrically connected to the internal electrode.
3. The electronic device according to claim 1, wherein the
electronic device is a multilayer ceramic capacitor.
4. The electronic device according to claim 1, wherein the Cu
plating layer has an average particle diameter of 3.0 to 5.0
.mu.m.
5. The electronic device according to claim 1, wherein the at least
one upper-side plating layer is a Ni plating layer.
6. The electronic device according to claim 5, further comprising
an Sn plating layer formed on the Ni plating layer.
Description
FIELD OF THE INVENTION
The present invention relates to an electronic device and a method
for manufacturing the same, and more particularly, relates to an
electronic device having the structure in which an external
electrode is formed on a surface of an electronic device main body
and to a method for manufacturing the electronic device.
BACKGROUND OF THE INVENTION
For example, as shown in FIG. 2, a multilayer ceramic capacitor,
one of representative ceramic electronic devices, has a ceramic
element 54 and two external electrodes 55a and 55b provided on two
end portions thereof. The ceramic element 54 has internal
electrodes (such as Ni electrodes) 51 which are disposed to face
each other with ceramic layers 52 interposed therebetween and which
are alternately extended to two end surfaces 53a and 53b located in
opposite directions, so that the two external electrodes 55a and
55b are electrically connected to the internal electrodes 51.
In addition, the external electrodes 55a and 55b are formed, for
example, by the steps of applying a conductive paste (Cu paste in
this case) to the ceramic element 54, then baking the conductive
paste to form Cu-baked electrode layers 56a and 56b, forming Ni
plating layers 57a and 57b on the Cu-baked electrode layers 56a and
56b to prevent dissolution by solder, and further forming Sn
plating layers 58a and 58b on the Ni plating layers 57a and 57b in
order to improve solder wettability, and hence the external
electrodes 55a and 55b have a three-layered structure composed of
the Cu-baked electrode layers 56a and 56b used as an underlayer,
the Ni plating layers 57a and 57b used as an interlayer, and the Sn
plating layers 58a and 58b used as an upper layer (surface layer),
respectively.
Although the Ni plating layers 57a and 57b are to be used as an
interlayer function to prevent entry of a Sn plating solution and
moisture of external environment, since minute voids are inherently
present in the Ni plating layers 57a and 57b, the function of
preventing the entry of a plating solution and moisture is not
satisfactory.
Accordingly, in order to prevent the entry of a plating solution
and moisture, the Cu-baked electrode layer must be formed in a
dense state by baking. However, in a baking step in which the
Cu-baked electrode layer is densified by baking, glass moves up to
the surface of the Cu-baked electrode layer and precipitates
thereon, thereby, for example, causing a plating defect in a
subsequent step of forming the Ni plating layers 57a and 57b and/or
causing solder popping in a mounting step (soldering step) due to
degradation in denseness of the Ni plating layer. As described
above, the defects caused by so called "glass scum"
disadvantageously occur.
Accordingly, in order to solve the above problems, a method has
been proposed (for example, in Patent Document 1) to obtain a baked
electrode which can be densified and which has good plating
properties by optimizing an electrode material.
In this method, a conductive paste is used which contains a
powdered metal primarily composed of a powdered Cu including a
flake-shaped Cu powder having a specific surface area, a long
diameter, and a thickness, which meet respective specifications,
and a spherical-shaped Cu powder at a predetermined ratio; a glass
powder; a binder; and an organic solvent, and external electrodes
are formed by applying this conductive paste on predetermined
regions of a ceramic element, followed by baking.
In addition, according to this method, it is described that
external electrodes can be formed which have an appropriate
denseness and which are able to prevent precipitation of a glass
component (binding agent) on the surface and the entry of a plating
solution inside the ceramic element.
However, since this method is liable to be influenced by the
changes in electrode material and process, it is not easy to ensure
sufficient reliability, and in addition to that, there has been a
problem in that higher-level requirements in the future cannot be
easily satisfied.
In addition, as another conventional technique, an electronic
device has been proposed (for example, in Patent Document 2) in
which as shown in FIGS. 3(a) and (b), as external electrodes 64
provided for an electronic device main body 65 having internal
electrodes 61 disposed therein, external electrodes are formed each
having a four-layered structure composed of a Cu-baked electrode
layer 66, a Cu plating layer 67, a Ni plating layer 68, and a
noble-metal plating layer 69.
That is, in this electronic device, the external electrodes 64 each
have a four-layered structure composed of a first external
electrode layer (Cu-baked electrode layer 66) formed by baking a
past containing powdered Cu or a powdered Cu alloy, a second
external electrode layer (Cu plating layer 67) of a Cu plating film
formed on the first external electrode layer, a third external
electrode layer (Ni plating layer 68) of a Ni plating film formed
on the second external electrode layer, and a fourth external
electrode layer (noble-metal plating layer 69) of a noble-metal
plating film formed on the third external electrode layer.
However, in the case of this Patent Document 2, since minute voids
are generally present in the Cu plating layer 67, the entry of a
plating solution and moisture of external environment cannot be
always sufficiently prevented, and as a result, there has been a
problem of inferior reliability. Patent Document 1: Japanese
Unexamined Patent Application Publication No. 2004-172383 Patent
Document 2: Japanese Unexamined Patent Application Publication No.
2004-55679
SUMMARY OF THE INVENTION
The present invention is conceived to solve the above problems, and
an object of the present invention is to provide a highly reliable
electronic device and a method for manufacturing the same, the
electronic device preventing entry of a plating solution via an
external electrode and entry of moisture of external environment
inside thereof, and generating no soldering defects nor solder
popping defects which are caused by precipitation of a glass
component on a surface of the external electrode.
To this end, an electronic device according to the present
invention comprises: an electronic device main body; and an
external electrode formed on a surface of the electronic device
main body, and in this electronic device, the external electrode
includes: a Cu-baked electrode layer primarily composed of Cu; a Cu
plating layer which is formed on the Cu-baked electrode layer and
which is processed by a recrystallization treatment; and at least
one upper-side plating layer formed on the Cu plating layer which
is processed by the recrystallization treatment.
In addition, the electronic device main body includes a ceramic
sintered body and an internal electrode disposed therein, and the
external electrode is electrically connected to the internal
electrode.
In addition, there is provided a method for manufacturing an
electronic device which includes: an electronic device main body;
and an external electrode formed on a surface of the electronic
device main body, the external electrode having a Cu-baked
electrode layer primarily composed of Cu; a Cu plating layer which
is formed on the Cu-baked electrode layer; and at least one
upper-side plating layer formed on the Cu plating layer. The method
for manufacturing an electronic device, described above,
comprises:
a step of applying a conductive paste containing glass and a Cu
powder as a primary component to the electronic device main body,
followed by baking at a predetermined baking temperature, to form
the Cu-baked electrode layer;
a step of precipitating Cu on the Cu-baked electrode layer to form
the Cu plating layer;
a step of performing a heat treatment at a temperature in the range
of a temperature at which the Cu plating layer is recrystallized to
a temperature at which the glass contained in the conductive paste
is not softened (both inclusive) so as to recrystallize the Cu
plating layer; and
a step of further precipitating a metal on the Cu plating layer to
form the upper-side plating layer.
The electronic device of the present invention is an electronic
device having an electronic device main body and an external
electrode provided on a surface of the electronic device main body,
and the external electrode includes: a Cu-baked electrode layer
primarily composed of Cu; a Cu plating layer which is formed on the
Cu-baked electrode layer and which is processed by a
recrystallization treatment; and at least one upper-side plating
layer formed on the Cu plating layer which is processed by the
recrystallization treatment. Since the texture of the Cu plating
layer processed by the recrystallization treatment is dense, a
highly reliable electronic device can be obtained that is able to
prevent the entry of a plating solution inside a ceramic element
via the external electrode and entry of moisture of external
environment inside thereof.
In addition, instead of preventing the entry of a plating solution
and moisture of external environment by a dense Cu-baked electrode
layer obtained by baking, since the Cu plating layer processed by
the recrystallization treatment is provided, the entry of a plating
solution and moisture in external environment is prevented by the
dense Cu plating layer obtained by the recrystallization.
Accordingly, the generation of so-called "glass scum" can be
suppressed in which a glass component moves to and precipitates on
the surface of the Cu-baked electrode layer when baking is
excessively carried out to obtain a dense Cu-baked electrode layer.
Hence, as a result, the generation of defects, such as plating
defects in a subsequent plating step (such as a Ni plating step or
a solder plating step) for forming the upper-side plating layer
and/or solder popping defects caused by degradation in denseness of
a plating layer to be formed, can be suppressed or prevented.
In addition, when the electronic device main body has a ceramic
sintered body and an internal electrode provided therein, and when
the external electrode is electrically connected to the internal
electrode, the internal electrodes are prevented from being damaged
by the entry of a plating solution inside the electronic device
main body, and properties are prevented from being degraded by the
entry of moisture of external environment inside the electronic
device main body; hence, a highly reliable electronic device (such
as a multilayer ceramic capacitor) can be provided.
In addition, the method for manufacturing an electronic device
according to the present invention comprises a step of applying a
conductive paste containing glass and a Cu powder as a primary
component to the electronic device main body, followed by baking at
a predetermined baking temperature, to form the Cu-baked electrode
layer; a step of precipitating Cu on the Cu-baked electrode layer
to form the Cu plating layer; a step of performing a heat treatment
at a temperature in the range of a temperature at which the Cu
plating layer is recrystallized to a temperature at which the glass
contained in the conductive paste is not softened (both inclusive)
so as to recrystallize the Cu plating layer; and a step of further
precipitating a metal on the Cu plating layer to form the
upper-side plating layer. Hence, an electronic device having an
external electrode disposed on a surface of the electronic device
main body can be efficiently manufactured, the external electrode
including the Cu-baked electrode layer primarily composed of Cu;
the Cu plating layer formed on the Cu-baked electrode layer; and at
least one upper-side plating layer formed on the Cu plating
layer.
That is, according to the method for manufacturing an electronic
device of the present invention, a highly reliable electronic
device can be efficiently manufactured which has an external
electrode capable of preventing the entry of a plating solution and
moisture of external environment inside thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view showing the structure of an
electronic device (multilayer ceramic capacitor) of one embodiment
according to the present invention.
FIG. 2 is a cross-sectional view showing the structure of a
conventional electronic device (multilayer ceramic capacitor).
FIG. 3(a) is a cross-sectional view showing the structure of
another conventional electronic device (multilayer ceramic
capacitor), and FIG. 3(b) is an enlarged cross-sectional view of an
important portion.
REFERENCE NUMERALS
1 internal electrode 2 ceramic layer 3a, 3b end surface 4 ceramic
element (electronic device main body) 5a, 5b external electrode 6a,
6b Cu-baked electrode layer 7a, 7b Cu plating layer 8a, 8b Ni
Plating layer 9a, 9b Sn plating layer
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, with reference to examples of the present invention,
features of the present invention will be described in more
detail.
EXAMPLE 1
FIG. 1 is a cross-sectional view showing the structure of an
electronic device (multilayer ceramic capacitor in this example)
manufactured by a method for manufacturing an electronic device
according to an example (example 1) of the present invention.
This multilayer ceramic capacitor is composed of two external
electrodes 5a and 5b and a ceramic element (electronic device main
body) 4 having internal electrodes (such as Ni electrodes) 1 which
are disposed to face each other with ceramic layers 2 interposed
therebetween and which are alternately extended to opposite end
surfaces 3a and 3b, and the two external electrodes 5a and 5b are
provided for the ceramic element 4 so as to be electrically
connected to the internal electrodes 1.
In addition, in the multilayer ceramic capacitor of this example,
the external electrodes 5a and 5b have a four-layered structure
including Cu-baked electrode layers 6a and 6b, Cu plating layers 7a
and 7b formed thereon, Ni plating layers 8a and 8b for preventing
dissolution by solder, and Sn plating layers 9a and 9b formed
thereon for improving solder wettability, respectively.
Hereinafter, a method for manufacturing this multilayer ceramic
capacitor will be described.
(1) First, after powdered Cu and a glass frit primarily composed of
a ZnO--B.sub.2O.sub.3--SiO.sub.2-based glass were mixed together,
an appropriate amount of an organic vehicle was added thereto, and
a mixture thus obtained was mixed and dispersed using a three-roll
mixer to form a conductive paste. The glass used in this example
was a glass having a softening point slightly higher than
600.degree. C.
(2) Next, two end surface sides of the fired ceramic element
(electronic device main body) 4 were immersed in the conductive
paste so as to be coated therewith, and drying was then
performed.
(3) Subsequently, by baking the conductive paste at 800.degree. C.
for 5 minutes in a nitrogen atmosphere, the Cu-baked electrode
layers 6a and 6b were formed.
(4) Next, Cu electroplating was performed, so that the Cu plating
layers 7a and 7b were formed on the Cu-baked electrode layers 6a
and 6b, respectively.
(5) Subsequently, a heat treatment was performed under
predetermined conditions in a nitrogen atmosphere, so that a
recrystallization treatment was performed for the Cu plating layers
7a and 7b.
(6) Next, Ni electroplating was performed, so that the Ni plating
layers 8a and 8b were formed on the Cu plating layers 7a and 7b,
respectively, in order to prevent dissolution by solder.
(7) Furthermore, Sn plating layer 9a and 9b were formed on the
above Ni plating layers 8a and 8b, respectively, so as to improve
solder wettability.
Accordingly, multilayer ceramic capacitors (samples) each having
the external electrodes 5a and 5b of a four-layered structure as
shown in FIG. 1 were obtained.
In addition, for comparison purpose, multilayer ceramic capacitors
(samples of comparative examples) were formed without a heat
treatment (recrystallization treatment) or with a heat treatment
(recrystallization treatment) which did not satisfy the conditions
of the present invention.
The structures of the samples of the examples and the comparative
examples were as follows.
TABLE-US-00001 Dimensions: length: 2.0 mm, width: 1.25 mm, height:
1.25 mm Dielectric ceramic: BiTiO.sub.3-based dielectric ceramic
Number of laminated internal 400 electrodes: Material for internal
electrode: Ni Structure of external electrode: Cu-baked electrode
layer (underlayer electrode)/Cu plating layer/Ni plating layer/Sn
plating layer Atmosphere for heat treatment nitrogen atmosphere
(recrystallization treatment) of Cu plating layer:
Subsequently, a plating test, a reliability test (PCBT test), and a
solder popping test were performed in accordance with the following
methods for the multilayer ceramic capacitors thus prepared.
[Plating Test]
For 100 samples (multilayer ceramic capacitors) of each example,
the plating test was performed in which after the Sn plating layer
was peeled away from the electrode using a stripping agent, the
surface thereof was observed by a stereo microscope (magnification:
50 times). In addition, after the Sn plating layer was peeled away,
a sample having a spot on the electrode surface at which the Ni
plating layer was not formed was counted as a defective.
[Reliability Test (PCBT Test)]
As for the reliability test (PCBT test), after 72 samples
(multilayer ceramic capacitors) of each example were mounted on a
substrate using a SnZnBi solder, the solder was remelted so that
the multilayer ceramic capacitors were removed from the substrate,
followed by a PCBT test performed at 125.degree. C., 95% Rh, and a
rated voltage for 72 hours. Subsequently, a sample having an
insulating resistance lower than its initial value was counted as a
defective.
[Solder Popping Test]
The solder popping test was performed such that after 500 samples
(multilayer ceramic capacitors) of each example were mounted on a
substrate on which SnPb eutectic solder was printed, reflow
mounting was performed, and the substrate was then observed by a
stereo microscope (magnification: 50 times). A sample in which a
solder ball was popped away was counted as a defective.
The results are shown in Table 1.
TABLE-US-00002 TABLE 1 Generation of Generation of Heat Treatment
Average Particle Defects in Plating Defects in Generation of
Defects (Recrystallization Diameter of Test Reliability Test (# in
Solder Popping Test Treatment) Conditions Particles of Cu (# of
defectives/ of defectives/ (# of defectives/total (.degree. C./min)
Plating Layer (.mu.m) total #) total #) #) Example 1 400/20 3.0
0/100 22/72 0/500 Example 2 500/20 4.0 0/100 7/72 0/500 Example 3
600/20 5.0 0/100 0/72 0/500 Comparative No heat treatment 0.5 0/100
72/72 0/500 Example 1 Comparative 200/20 1.0 0/100 72/72 0/500
Example 2 Comparative 700/20 6.0 2/100 24/72 3/500 Example 3
As shown in Table 1, in the case of the multilayer ceramic
capacitors of comparative example 1 which were not processed by the
heat treatment (recrystallization treatment), defects were observed
in all of 72 samples in the reliability test (PCBT test) The reason
for this is believed that the particles of the Cu plating layer
were not recrystallized, and hence densification thereof was not
advanced.
In addition, as shown in Table 1, also in the case of the
multilayer ceramic capacitors of comparative example 2 which were
processed by a heat treatment at 200.degree. C., defects were also
observed in all of 72 samples in the reliability test (PCBT test)
as in the case of comparative example 1 in which the heat treatment
(recrystallization treatment) was not performed. The reason for
this is believed that since the temperature was low by a heat
treatment at 200.degree. C. for 20 minutes, although the average
particle diameter of the Cu particles forming the Cu plating layer
was increased to a certain extent, it was not grown large as
compared to that obtained by recrystallization, and as a result,
densification of the Cu plating layer was not advanced.
In addition, as shown in Table 1, in the case of the multilayer
ceramic capacitors of comparative example 3 which were processed by
a heat treatment (recrystallization treatment) at 700.degree. C.,
the number of defectives was decreased to 24 out of 72 samples in
the reliability test (PCBT test) as compared to that of comparative
example 1 in which the heat treatment (recrystallization treatment)
was not performed and to that of comparative example 2 in which the
heat treatment was performed at 200.degree. C., a temperature lower
than the recrystallization temperature, for 20 minutes. However,
the number of defectives in the plating test was 2 out of 100
samples, and the number of defectives was 3 out of 500 samples in
the solder popping test; hence, preferable results could not be
obtained. The reason for this is believed that although the
particles of the Cu plating layer could be recrystallized by the
heat treatment at 700.degree. C. for 20 minutes, due to softening
of glass contained in the Cu-baked electrode layer, the glass
flowed out, and as a result, sealing properties were degraded. In
addition, it is also believed that as the Cu-baked electrode was
being sintered, the glass moved to (or precipitated on) the surface
of the Cu plating layer, and hence defects, such as plating defects
and solder popping defects, occurred besides degradation in
reliability. In addition, under the heat treatment conditions in
comparative example 3 at 700.degree. C. for 20 minutes, since the
surface of the Cu plating layer was oxidized to a certain extent
due to a high temperature, Ni plating properties were degraded, and
thereby the denseness of the Ni plating layer was also degraded;
hence, it is also believed that this degradation in denseness was
also partly responsible for the generation of the solder popping
defect.
On the other hand, in the cases of the multilayer ceramic
capacitors of examples 1 to 3 in which the heat treatments
(recrystallization treatments) were performed at 400.degree. C. for
20 minutes (example 1), at 500.degree. C. for 20 minutes (example
2), and at 600.degree. C. for 20 minutes (example 3), the results
of the plating test, the reliability test, and the solder popping
test were all superior, and hence it was confirmed that a
multilayer ceramic capacitor having desired properties could be
obtained.
In particular, in the case of the multilayer ceramic capacitors of
example 3 in which the heat treatment (recrystallization treatment)
was performed at 600.degree. C. for 20 minutes (example 3), in all
of the plating test, the reliability test, and the solder popping
test, no defects were observed, and hence the most preferable
result was obtained. The reasons for this are believed that in the
heat treatment performed at 400.degree. C. (example 1) and at
500.degree. C. (example 2), a Cu plating layer having a dense
texture capable of completely preventing the entry of a plating
solution and moisture could not be obtained, and that on the other
hand, when the heat treatment temperature was increased to
600.degree. C., the recrystallization of the Cu plating layer was
further advanced, and the texture thereof was changed to a more
dense structure.
In the examples described above, although the multilayer ceramic
capacitors are described by way of example, the present invention
can be applied to, besides the multilayer ceramic capacitor,
various electronic devices each having external electrodes provided
on surfaces of a electronic device main body, such as a multilayer
varistor, a multilayer LC composite device, and a multilayer
circuit substrate. Also in this case, an effect similar to that of
the above examples can be obtained.
In addition, in the above examples, although the Ni plating layer
and the Sn plating layer are formed on the Cu plating layer
processed by a heat treatment (recrystallization treatment), the
type and the number of the upper-side plating layers formed on the
Cu plating layer processed by a heat treatment (recrystallization
treatment) are not particularly limited, and for example, after a
Ni plating layer is formed on the Cu plating layer processed by a
heat treatment (recrystallization treatment), a Sn--Pb plating
layer may be formed on the Ni plating layer instead of the Sn
plating layer of the examples.
In addition, the other points of the present invention are not also
limited to the above examples, and the types of materials forming
an electronic device main body, concrete structures thereof,
materials forming internal electrodes, the presence or the absence
thereof, and the like may be variously changed and modified without
departing from the spirit and the scope of the present
invention.
As has thus been described, according to the present invention,
since the Cu plating layer formed on the Cu-baked electrode layer
is recrystallized by a heat treatment performed at a temperature in
the range of a temperature at which the Cu plating layer is
recrystallized to a temperature at which the glass contained in the
conductive paste is not softened (both inclusive), and the Cu
plating layer thus processed by the recrystallization treatment has
a dense texture, a highly reliable ceramic electronic device
capable of preventing the entry of a plating solution and moisture
of external environment inside a ceramic element via external
electrodes can be obtained.
In addition, since it is not necessary to form a dense Cu-baked
electrode layer by baking, the generation of defects, such as
plating defects and solder popping defects caused by degradation in
denseness of the plating layer, can be suppressed or prevented.
Accordingly, the present invention can be widely applied to various
electronic devices having the structure in which an external
electrode is provided on a surface of an electronic device main
body and to methods for manufacturing the above electronic
devices.
* * * * *